Integrated Biological Gas Scrubbing and Digester Gas Mixing System at HL Handa & Co's WWTP

Municipal wastewater digesters generate biogas containing hydrogen sulfide and odorous compounds that pose corrosion, safety, and environmental risks. Additionally, uneven gas distribution within digesters can lead to stratification, scum formation, and reduced biological efficiency. The client required a solution capable of simultaneously removing H₂S and odors while ensuring uniform biogas mixing, all under low-pressure conditions and variable operating loads typical of sewage treatment plants.

CRA engineered an integrated biological gas treatment and mixing solution tailored for municipal wastewater operations. The system combines a biological gas scrubber for contaminant removal with a dedicated digester gas mixing arrangement to enhance process stability and digester performance.

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Core Systems Delivered:

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• Biological gas scrubber with controlled bioactivity for H₂S and odor removal
• Digester gas mixing system for uniform gas distribution
• Integrated piping, instrumentation, and control interfaces
• Skid-based modular construction for ease of installation

The system was engineered with a focus on reliable biological H₂S removal and effective gas homogenization, ensuring stable operation under low-pressure and variable-load conditions typical of municipal wastewater digesters.

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• Scrubber sizing and biological media selection optimized for 175 Nm³/hr biogas flow
• Gas mixing configuration designed to ensure uniform distribution within the digester
• Low-pressure system architecture suitable for 20 mbar(g) operation
• Design margins incorporated to handle normal and upset operating conditions
• Integration-focused layout enabling compatibility with existing digester infrastructure

The system components were manufactured under controlled conditions with defined quality checks to ensure dimensional accuracy, material integrity, and compliance with municipal wastewater and biogas service requirements.

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• In-house fabrication of scrubber vessels, internals, and gas mixing components
• Material selection and workmanship aligned with biogas and corrosive service conditions
• Dimensional, visual, and functional inspections at each fabrication stage
• Quality checks on piping, instrumentation, and skid assemblies
• Documentation and traceability maintained for manufacturing and inspection activities

The integrated biological scrubbing and gas mixing system delivered stable H₂S removal and uniform digester gas distribution, improving overall digester reliability under low-pressure municipal operating conditions.

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• Consistent reduction of H₂S and odorous compounds from digester gas
• Uniform biogas mixing, preventing stratification and scum formation
• Stable performance under variable gas flow and load conditions
• Improved biological activity and digester process efficiency
• Enhanced protection of downstream biogas handling equipment

This project demonstrates CRA’s capability to deliver integrated biological gas treatment and digester mixing solutions for municipal wastewater applications. By combining biological scrubbing with engineered gas mixing, CRA provided H. L. Handa & Company with a robust, low-pressure system that enhances digester performance, odor control, and long-term operational reliability while meeting environmental and safety expectations.